Constellation rotation relay system and constellation rotation relay method

ABSTRACT

Provided is a constellation rotation relay system and constellation rotation relay method which can acquire full diversity gain by performing constellation rotation for a channel matrix in a relay network when configuring a virtual MIMO channel. The constellation rotation system includes a matrix creator for creating a symbol matrix by configuring a symbol transmitted in parallel from a source of a relay network; and a constellation rotation unit constellation rotating the symbol in the symbol matrix by adding a constellation rotation matrix to the created symbol matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/708,457, filed Feb. 21, 2007, which claims the benefit under 35U.S.C. §119(a) of a Korean Patent Application No. 10-2006-0087005, filedon Sep. 8, 2006, in the Korean Intellectual Property Office, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a constellation rotation relay systemand a constellation rotation relay method thereof. More particularly,the present invention relates to a constellation rotation relay systemand a constellation rotation relay method which can acquire fulldiversity gain by performing a constellation rotation process for achannel matrix in a relay network, when configuring a virtual multipleinput multiple output (MIMO) channel.

2. Description of Related Art

A relay network is used for maintaining communication in a shadow regionand extending a coverage area of a cell. Communication performancebetween a base station and a mobile station may be improved by employinga relay.

FIG. 1, parts i), ii), and iii) are diagrams illustrating an example ofa protocol applied to a relay network in related art.

As illustrated in FIG. 1 parts i), ii), and iii), there is a MIMO, asingle input multiple output (SIMO), and a multiple input single output(MISO) protocols provided in a conventional relay network.

In FIG. 1 parts i), ii), and iii), S, R, and D respectively indicate asource, a relay and a destination, and a dotted line indicates atransmission comprising different symbols.

FIG. 1 part i) relates to a MIMO protocol. A source in a first time slottransmits a first symbol to a relay and a destination. Also, the sourcein a second time slot transmits a second symbol to the destination, andthe relay transmits the symbol, received in the first time slot, to thedestination by applying an amplify-and-forward (AF) or adecode-and-forward (DF) function. In the AF function the received symbolis power amplified in the relay and then retransmitted. In the DFfunction, the received symbol is decoded and then re-encoded. There-encoded symbol is then power amplified and transmitted.

FIG. 1 part ii) relates to a SIMO protocol. Operation in a first timeslot is identical to the MIMO protocol, and a relay operates identicalto the MIMO protocol, however the source in a second time slot does notoperate.

FIG. 1 part iii) relates to a MISO protocol. A source in a first timeslot transmits a first symbol to a relay, the source in a second timeslot retransmits the first symbol, and the relay transmits the symbol,received in the first time slot, to a destination by applying the AFfunction or the DF function.

As shown in Equation 1, the MIMO protocol has an advantage of having atwice the transmission rate of the SIMO protocol and the MISO protocol.

y _(R,1) =h _(SR) x ₁ +n _(R,1)

y _(D,1) =h _(SD) x ₁ +n _(D,1)

y _(D,2) =h _(RD) {circumflex over (x)} ₁ +h _(SD) x ₂ +n _(D,2)

Equation 1 indicates input/output equations in a relay and a destinationwith respect to the MIMO protocol using the DF system. The S, R and D inEquation 1 respectively indicates a source, a relay and a destination,and the subscripts “1” and “2” indicate a time slot. Also, y indicates areceiving signal, x indicates an input signal, h indicates a channelvalue, n indicates white noise, and {circumflex over (x)}₁ indicates adecoded symbol.

$\begin{matrix}{\begin{bmatrix}y_{D,1} \\y_{D,2}\end{bmatrix} = {\left. {{\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}} + \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}\rightarrow Y \right. = {{Hx} + N}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

When Equation 1 is represented into a matrix, Equation 1 is representedas Equation 2. In Equation 2, when the relay decodes the symbol to x₁via a perfect decoding process, ‘{circumflex over (x)}₁=x₁’ may betenable. Accordingly, the MIMO protocol may configure a virtual MIMOchannel environment as shown in Equation 2.

In Equation 2, conversely, a conventional MIMO system, one of thechannel values of the channel matrix H becomes ‘0’, subsequently fulldiversity gain may not be acquired. Only a first order diversity in thevirtual MIMO channel environment by the MIMO protocol may be gained dueto the ‘0’ channel value even if a signal-to-noise ratio with respect toa link between the source and the relay is greater.

Accordingly, a new relay system which can constellation rotate a channelvalue by multiplying the constellation with a predetermined matrix, andthereby may acquire full diversity gain when configuring a virtual MIMOequivalence channel, is required.

SUMMARY OF THE INVENTION

An aspect of exemplary embodiments of the present invention is toaddress at least the above problems and/or disadvantages and to provideat least the advantages described below. Accordingly, an aspect ofexemplary embodiments of the present invention is to provide aconstellation relay system and a constellation relay method whichinduces a channel in a channel matrix to prevent a ‘0’ value byconstellation rotating a symbol, transmitted from a source, whenconfiguring a virtual MIMO channel.

An aspect of exemplary embodiments of the present invention alsoprovides a constellation relay system and a constellation relay methodwhich can induce a channel in a channel matrix to prevent a ‘0’ value byconstellation rotating the channel, used in transmitting the symbol to adestination, and acquiring full diversity gain.

An aspect of exemplary embodiments of the present invention alsoprovides a constellation relay system and a constellation relay methodwhich can acquire both a higher data transmission rate and fulldiversity gain by compensating for a decrease of diversity gain of aprotocol whose data transmission rate is comparatively greater withconstellation rotation, and subsequently, performance of a relay networkmay be enhanced.

According to an aspect of exemplary embodiments of the presentinvention, there is a constellation rotation relay system including amatrix creator for creating a symbol matrix by configuring a symboltransmitted in parallel from a source of a relay network; and aconstellation rotation unit for constellation rotating the symbol in thesymbol matrix by adding a constellation rotation matrix to the createdsymbol matrix.

According to another aspect of exemplary embodiments of the presentinvention, there is a constellation rotation relay system including amatrix creator creating a channel matrix by configuring a link channel,used by the symbol to be transmitted in parallel to the destination ofthe relay network; and a constellation rotation unit constellationrotating a channel in the channel matrix by adding a constellationrotation matrix to the created channel matrix.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following detailed description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 parts i), ii), and iii) are diagrams illustrating examples ofprotocols applied to a relay network according to related art;

FIG. 2 is a diagram illustrating a specific configuration of aconstellation rotation relay system according to an exemplary embodimentof the present invention;

FIG. 3 parts i) and ii) are diagrams illustrating an example of creatingmatrixes of a matrix creator according to an exemplary embodiment of thepresent invention;

FIG. 4 is a flowchart illustrating a constellation rotation relay methodaccording to an exemplary embodiment of the present invention; and

FIG. 5 is a flowchart illustrating a constellation rotation relay methodaccording to another exemplary embodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features, and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The matters defined in the description such as a detailed constructionand elements are provided to assist in a comprehensive understanding ofthe embodiments of the invention and are merely exemplary. Accordingly,those of ordinary skill in the art will recognize that various changesand modifications of the embodiments described herein can be madewithout departing from the scope and spirit of the invention. Also,descriptions of well-known functions and constructions are omitted forclarity and conciseness.

FIG. 2 is a diagram illustrating a specific configuration of aconstellation rotation relay system 200 according to an exemplaryembodiment of the present invention.

A relay network source includes a source, a relay, and a communicationnode of a destination, and is used to transmit a symbol from the sourceto the destination, located in a shadow area, via cooperation with therelay.

Via the relay network, the symbol, transmitted from the source, may betransmitted to an area where service would not be available with aconventional art, and subsequently cell coverage, i.e. an area where acommunication service is available, may be widely expanded.

The constellation rotation relay system 200 includes a function thatallows for a continuous communication service with signal processingamong the source in the relay network, the relay and the destination,and a function that constellation rotates a link of a channel, which isused in the symbol or in transmitting the symbol. The constellationrotation excludes a ‘0’ as a channel value for a channel matrix, whichis created in association with an input and an output of the symbol inthe destination, and subsequently may acquire full diversity gain in therelay network, when configuring a virtual MIMO channel.

The constellation rotation relay system 200 includes a matrix creator210 and a constellation rotation unit 220.

FIG. 1 parts i), ii), and iii) are diagrams illustrating examples of aprotocol applied to a relay network according to a related art.

The constellation rotation relay system 200 may be embodied in aplurality of exemplary embodiments with respect to constellationrotation, depending on a location of a communication node to which aconstellation matrix is added for constellation rotation.

Described below with reference to FIG. 2, is the scenario where a sourceis the communication node where the constellation rotation matrix isadded. Since constellation rotation is performed at the communicationnode where the constellation rotation matrix is added, hereconstellation rotation is performed at the source.

The source performs sequential processes to transmit the symbol to therelay or the destination in a wireless environment, e.g. a modulationprocess and an amplification process with respect to the symbol.

The matrix creator 210 performs the sequential processes to create asymbol matrix by configuring the symbol, transmitted in parallel fromthe source of the relay network. Namely, the matrix creator 210 arrangesthe symbol to create a matrix, based on a time slot transmitting singleindependent information. Specifically, the source may transmit a symbolx₁ in a first time slot and transmit a symbol x₂ in a second time slot,and the matrix creator 210 creates a symbol matrix

$\quad\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}$

by configuring the symbol in parallel.

The constellation rotation unit 220 constellation rotates the symbol inthe symbol matrix by adding a constellation rotation matrix to thecreated symbol matrix. Namely, the constellation rotation unit 220 mayprovide an environment preventing a ‘0’ value for a channel in a channelmatrix to be created in association with input/output of a symbol in asubsequent destination, by performing a constellation rotation processwith respect to the symbol transmitted from the source.

There are

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ $\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}$

in the present specification as examples of the constellation rotationmatrix to be added to the symbol matrix, the constellation rotation unit220 selects an optimal constellation rotation matrix depending on asystem environment among

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}.$

The constellation rotation unit 220 may select the variable ρ byconsidering a bit energy to a noise ratio, or a bit error rate (BER)when

$\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}$

is selected as the constellation rotation matrix. It is desirable thatthe constellation rotation unit 220 selects the variable ρ as ‘2.05’ byanalyzing a parameter in the constellation rotation matrix, showingsuperior second order diversity, when calculating with the channelmatrix.

As described above, the constellation rotation unit 220 performsconstellation rotation with respect to the symbol by multiplying theselected constellation rotation matrix

$\Theta \left( \begin{bmatrix}\theta_{11} & \theta_{12} \\\theta_{21} & \theta_{22}\end{bmatrix} \right)$

to a left side of the symbol matrix

$\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}{\quad.}$

Namely, the constellation rotation unit 220 may convert the symbolmatrix

$\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}\quad$

into the constellation rotated symbol matrix

$\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}{\quad.}$

Accordingly, the symbol constellation rotated in the first time slot{tilde over (x)}₁ is transmitted from the source to the relay and thedestination, and the symbol {tilde over (x)}₂ constellation rotated inthe second time slot is transmitted to the destination. Additionally,the relay generates the symbol {tilde over (x)}₁′ by performingdecoding/re-encoding {tilde over (x)}₁, and transmits to the generatedsymbol {tilde over (x)}₁′ to the destination in the second time slot.

With respect to the symbol transmission, equations associated withinput/output in the destination may be represented as,‘y_(D,1)=h_(SD)*{tilde over (x)}₁+n_(D,1)’ in the first time slot, and‘y_(D,2)=h_(RD)*{tilde over (x)}₁′+h_(SD)*{tilde over (x)}₂+n_(D,2)’ inthe second time slot. In this instance, y indicates a signal associatedwith reception in the destination, h indicates a channel value of thelink, and n indicates white noise in the destination.

Namely, the destination in the first time slot receives theconstellation rotated symbol {tilde over (x)}₁ through a link h_(SD)connected to the source, and the destination in the second time slotreceives the constellation rotated symbol {tilde over (x)}₂ through alink h_(SD) connected to the source and the symbol {tilde over (x)}₁′through a link h_(RD) connected to the relay.

Since the constellation rotated symbol {tilde over (x)}₁ is perfectlydecoded/re-encoded by the relay, when it is assumed that the symbol{tilde over (x)}₁′ is identical to the constellation rotated symbol{tilde over (x)}₁, input/output equations in the second time slot may berepresented as, ‘y_(D,2)=h_(RD)*{tilde over (x)}₁+h_(SD)*{tilde over(x)}₂+n_(D,2)’.

Under this assumption, the matrix creator 210 creates a channel matrixby configuring a link channel in parallel, the link channel being usedby the constellation rotated symbols {tilde over (x)}₁ and {tilde over(x)}₂ to be transmitted to the destination of the relay network.

The equation associated with the input/output equations in the first andsecond time slots may be represented as a matrix

${\begin{bmatrix}y_{D,1} \\y_{D,2}\end{bmatrix} = {{\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}} + \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}},$

and the matrix creator 210 creates

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\quad$

associated with the link channel into a channel matrix.

Also, the constellation rotation unit 220 constellation rotates thechannel in the channel matrix into another value except for ‘0’ byconsidering the constellation rotated symbol. Specifically, theconstellation rotation unit 220 interprets the constellation rotatedsymbol

$\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}\quad$

as

${\Theta \begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}},$

adds the constellation rotation matrix Θ to the channel matrix

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad,}$

and subsequently performs the constellation rotation process for thechannel matrix.

Specifically, the constellation rotation unit 220 interprets

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad\; {\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}{\quad\mspace{11mu} {{{as}\mspace{14mu}\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}}{\quad{{\Theta \begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}},}}}}}}$

through a matrix calculation of the channel matrix

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\quad$

with the constellation rotated channel matrix

$\begin{bmatrix}{\overset{\sim}{h}}_{11} & {\overset{\sim}{h}}_{12} \\{\overset{\sim}{h}}_{21} & {\overset{\sim}{h}}_{22}\end{bmatrix}.$

Accordingly, the constellation rotation unit 220 enables the channel inthe channel matrix to have another value excluding ‘0’.

Equations associated with the above described constellation rotation forthe channel matrix are represented as

$\begin{matrix}{\begin{bmatrix}y_{D,1} \\y_{D,2}\end{bmatrix} = {\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad{\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}{\quad{+ \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}}}}}} \\{= {\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad{{\Theta \begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}}{\quad{+ \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}}}}}} \\{= {{\begin{bmatrix}{\overset{\sim}{h}}_{11} & {\overset{\sim}{h}}_{12} \\{\overset{\sim}{h}}_{21} & {\overset{\sim}{h}}_{22}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}}{\quad{+ {\begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}.}}}}}\end{matrix}$

Accordingly, the constellation rotation system 200 of an exemplaryembodiment of the present invention which induces a channel in a channelmatrix to prevent a ‘0’ value by constellation rotating a symbol,transmitted from a source, when configuring a virtual MIMO channel, andhave full diversity gain.

Also, according to an exemplary embodiment of the present invention,both gain of a higher data transmission rate and full diversity gain maybe acquired by compensating for a decrease of diversity gain of aprotocol whose data transmission rate is comparatively greater withconstellation rotation, and subsequently performance of a relay networkmay be enhanced.

Described below is another exemplary embodiment of the presentinvention, wherein a destination is the communication node whereconstellation rotation is performed.

Initially, the matrix creator 210 creates a channel matrix byconfiguring a link channel in parallel, the link channel being used by aconstellation rotated symbol to be transmitted to the destination of therelay network. Namely, the matrix creator 210 checks input/output in thedestination in association with symbol transmission from the source orthe relay, and creates the channel matrix using the checked input/outputequations. Hereinafter, creation of the matrixes by the matrix creator210 is described by referring to FIG. 3.

FIG. 3 parts i) and ii) are diagrams illustrating an example of creatingmatrixes of a matrix creator 210 of FIG. 2.

In FIG. 3 part i), a symbol is transmitted between a source and adestination, the source and a relay, and the relay and the destinationaccording to the MIMO protocol described in FIG. 1.

The source performs processes to transmit the symbol to the relay or thedestination in a wireless environment, e.g. a modulation process and anamplification process. Hereinafter, the source may transmit themodulated symbol to the relay or the destination depending on apredetermined transmission request.

As shown in FIG. 3 part i), the source according to the MIMO protocolrespectively transmits the symbol x₁ to the relay and the destination ina first time slot. In this instance, input/output equations in thedestination in the first time slot in association with the symboltransmission may be represented as, ‘y_(D,1)=h_(SD)*x₁+n_(D,1)’. Namely,the destination in the first time slot receives only the symbol x₁through a link h_(SD) connected to the source. In this instance, n_(D,1)may indicate white noise generated in the destination in the first timeslot.

In the second time slot, the source transmits the symbol x₂ to thedestination in a second time slot, and the relay may transmit the symbolx₁, transmitted from the source, to the destination after improving thequality of the symbol x₁ by an amplify-and-forward (AF) function or adecode-and-forward (DF) function.

With respect to the symbol transmission, input/output equationsassociated with input/output in the destination may be represented as,‘y_(D,2)=h_(RD)*x₁+h_(SD)*x₂+n_(D,2)’. Specifically, the destination inthe second time slot receives the symbol x₁ through the link h_(SD)connected to the source and the link h_(RD) connected to the relay. Inthis instance, n_(D,2) may indicate white noise which occurs in thedestination in the second time slot.

In FIG. 3 ii), the input/output equations in each time slot may berepresented as a matrix type similar to a matrix before constellationrotation.

Namely, the input/output equations associated with the destination foreach time slot are represented as ‘y_(D,1)=h_(SD)*x₁+h_(D,1)’ and‘Y_(D,2)=h_(SD)*x₂+n_(D,2)’, and this may be configured as

$\begin{bmatrix}y_{D,1} \\y_{D,2}\end{bmatrix} = {\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad{\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}{\quad{+ \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}}}}}$

in parallel by the matrix creator 210.

Specifically, the matrix creator 210 of FIG. 2 creates a channel matrix

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\quad$

by converting the input/output equations into a matrix type in thedestination in association with the symbol transmission.

Referring back to FIG. 2, the constellation rotation unit 220constellation rotates the channel in the channel matrix by adding theconstellation rotation matrix to the created symbol matrix.Specifically, the constellation rotation unit 220 converts the channelin the channel matrix into another value except for ‘0’ through theconstellation rotation by the constellation rotation matrix, andsubsequently the channel matrix may be configured as a full matrix type.

There are

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{j\; {\pi/4}} \\1 & {- ^{j\; {\pi/4}}}\end{bmatrix},{{and}\mspace{14mu} {\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}}$

in the specification as examples of the constellation rotation matrix,and the constellation rotation unit 220 selects an optimal constellationrotation matrix according to a system environment among

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{j\; {\pi/4}} \\1 & {- ^{j\; {\pi/4}}}\end{bmatrix},{{and}\mspace{14mu} {{\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}.}}$

The constellation rotation unit 220 may select the variable ρ byconsidering a bit energy to a noise ratio, or a BER when

$\; {\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}$

is selected as the constellation rotation matrix. It is desirable thatthe constellation rotation unit 220 selects the variable ρ as ‘2.05’ byanalyzing a parameter in the constellation rotation matrix, showingsuperior second order diversity, when calculating with the channelmatrix.

In FIG. 3 part ii), after constellation rotation, a predeterminedconstellation rotation matrix Θ, selected by the constellation rotationunit 220, is added to a right side of the channel matrix

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}.$

Namely, the constellation rotation unit 220 may acquire a channel matrix

$\quad\begin{bmatrix}{\overset{\sim}{h}}_{11} & {\overset{\sim}{h}}_{12} \\{\overset{\sim}{h}}_{21} & {\overset{\sim}{h}}_{22}\end{bmatrix}$

by multiplying the constellation rotation matrix Θ with the channelmatrix

$\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}.$

Thus, according to an exemplary embodiment of the present invention, theconstellation rotation system 200 of FIG. 2 may induce a channel in achannel matrix to prevent a ‘0’ value for the channel, used intransmitting a symbol to a destination, when configuring a virtual MIMOchannel, and full diversity gain may be acquired.

Also, according to an exemplary embodiment of the present invention,both gain of a higher data transmission rate and full diversity gain maybe acquired by compensating for a decrease of diversity gain of aprotocol whose data transmission rate is comparatively greater withconstellation rotation, and subsequently, performance of a relay networkmay be enhanced.

Hereinafter, an operation flow of the constellation rotation system 200is described in detail.

FIG. 4 is a flowchart illustrating a constellation rotation relay methodaccording to an exemplary embodiment of the present invention.

The constellation rotation method may be performed by the abovedescribed constellation rotation system 200.

In operation 5410, the constellation rotation system 200 creates asymbol matrix by configuring a symbol, transmitted from a source of arelay network, in parallel. In operation 5410, the source performssequential processes to transmit the symbol to a relay or a destinationin a wireless environment, and the symbol matrix is created byconfiguring the symbol in parallel based on a time slot. Specifically,the source may transmit a symbol x₁ in a first time slot and transmit asymbol x₂ in a second time slot, and the constellation rotation relaysystem 200 creates the symbol matrix

$\quad\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}$

by configuring the symbol in parallel.

In operation 5420, the constellation rotation relay system 200constellation rotates the symbol in the symbol matrix by adding aconstellation rotation matrix to the created symbol matrix. Operation5420 enables the channel in the channel matrix to be created inassociation with an input/output of a symbol in a subsequent destinationto prevent a ‘0’ value by performing the constellation rotation processwith respect to the symbol transmitted from the source.

In operation 5420, the constellation rotation system 200 may select anyone of

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{j\; {\pi/4}} \\1 & {- ^{j\; {\pi/4}}}\end{bmatrix},{{and}\mspace{14mu} {{\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}.}}$

as the constellation rotation matrix to be added to the symbol matrix.

The constellation rotation relay system 200 may select the variable P byconsidering a bit energy to a noise ratio, or a BER when

$\; {\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}}$

is selected as the constellation rotation matrix. It is desirable thatthe constellation rotation relay system 200 selects the variable ρ as‘2.05’ by analyzing a parameter in the constellation rotation matrix,showing superior second order diversity, when calculating with thechannel matrix.

Namely, the constellation rotation relay system 200 may convert thesymbol matrix

$\quad\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}$

into the constellation rotated symbol matrix

$\quad\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}$

by performing constellation rotation by multiplying the constellationrotation matrix by the symbol matrix.

In operation S430, the constellation rotation relay system 200 transmitsthe constellation rotated symbol to the relay or the destination fromthe source based on a predetermined protocol. Specifically, in operationS430, the constellation rotation relay system 200 may transmit thesymbol {tilde over (x)}₁, constellation rotated in a first time slot,from the source to the relay and the destination, and transmit thesymbol {tilde over (x)}², constellation rotated in a second time slot,from the source to the destination. Additionally, the relay generates are-encoded symbol {tilde over (x)}₁′ by performing decoding/re-encodingof the constellation rotated symbol {tilde over (x)}₁ in a DF operation,and transmits the symbol {tilde over (x)}₁′ generated in the second timeslot to the destination.

In operation S440, the constellation rotation relay system 200 creates achannel matrix by configuring a link channel, used by the constellationrotated symbol to be transmitted to the destination of a relay network,in parallel. In the operation S440, with respect to the symboltransmission, the channel matrix associated with the link channel iscreated by representing input/output equations in the destination as amatrix. Specifically, the constellation rotation relay system 200creates

$\quad\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}$

associated with the link channel as the channel matrix when theinput/output equations in the destination are represented as

$\begin{bmatrix}y_{D{.1}} \\y_{D{.2}}\end{bmatrix} = {\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}{\quad{\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix} + {\begin{bmatrix}n_{D{.1}} \\n_{D{.2}}\end{bmatrix}.}}}}$

In operation S450, the constellation rotation relay system 200constellation rotates the channel in the channel matrix into anothervalue except for ‘0’ according to the constellation rotated symbol.Specifically, the constellation rotation relay system 200 interprets theconstellation rotated symbol

$\quad\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}$

as

$\Theta {\quad{\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix},}}$

adds the constellation rotation matrix Θ to the channel matrix

$\quad{\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix},}$

and subsequently performs the constellation rotation process for thechannel matrix.

According to the constellation rotation, the constellation rotationrelay system 200 may convert the channel matrix

$\quad\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}$

into the constellation rotated channel matrix

$\quad{\begin{bmatrix}{\overset{\sim}{h}}_{11} & {\overset{\sim}{h}}_{12} \\{\overset{\sim}{h}}_{21} & {\overset{\sim}{h}}_{22}\end{bmatrix},}$

and consequently the channel in the channel matrix may have anothervalue except for ‘0’.

Accordingly, the constellation rotation relay system 200 of an exemplaryembodiment of the present invention may induce a channel in a channelmatrix to prevent a ‘0’ value by constellation rotating a symbol,transmitted from the source, when configuring a virtual MIMO channel,and full diversity gain is acquired.

Also, the constellation rotation relay system 200 of an exemplaryembodiment of the present invention may acquire both gain of a higherdata transmission rate and full diversity gain by compensating for adecrease of diversity gain of a protocol whose data transmission rate iscomparatively greater with constellation rotation, and subsequentlyperformance of a relay network may be enhanced.

FIG. 5 is a flowchart illustrating a constellation rotation relay methodaccording to another exemplary embodiment of the present invention.

Operations of the constellation rotation relay system 200 described withreference to FIG. 5 are for the scenario where a destination is thecommunication node where a constellation rotation matrix is added.

In operation 5510, the constellation rotation relay system 200 creates achannel matrix by configuring a link channel in parallel, the linkchannel being used by a symbol to be transmitted to a destination of arelay network. The operation 5510 checks an input/output in thedestination in association with a symbol transmission from a source or arelay, and creates the channel matrix using the checked input/output.Specifically, when the input/output equations in each time slot arerepresented as ‘y_(D,1)=h_(SD)*x₁+n_(D,1)’ and‘Y_(D,2)=h_(RD)*x₁+h_(SD)*x₂+n_(D,2)’, the constellation rotation relaysystem 200 converts the input/output equations into a matrix type

$\begin{bmatrix}y_{D,1} \\y_{D,2}\end{bmatrix} = {{\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}} + \begin{bmatrix}n_{D,1} \\n_{D,2}\end{bmatrix}}$

by configuring the input/output equations in parallel. Accordingly, theconstellation rotation relay system 200 may create

$\quad\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}$

as the channel matrix.

In operation S520, the constellation rotation relay system 200constellation rotates the channel in the channel matrix by adding theconstellation rotation matrix to the created channel matrix.Accordingly, the constellation rotation relay system 200 may overcome aproblem with the conventional art, in which only first order diversityis acquired, since the constellation rotation relay system 200 convertsthe channel in the channel matrix into another value except for ‘0’through the constellation rotation.

In the operation 5520, the constellation rotation relay system 200 mayselect an optimal constellation rotation matrix among

$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}},$

the variable ρ indicating ‘2.05’.

Specifically, the constellation rotation relay system 200 may acquirethe constellation rotated channel matrix

$\quad\begin{bmatrix}{\overset{\sim}{h}}_{11} & {\overset{\sim}{h}}_{12} \\{\overset{\sim}{h}}_{21} & {\overset{\sim}{h}}_{22}\end{bmatrix}$

by adding a predetermined constellation rotation matrix Θ to a rightside of the channel matrix

$\quad{\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix},}$

and consequently the channel matrix becomes a full matrix, without a ‘0’channel.

Thus, according to an exemplary embodiment of the present invention, theconstellation rotation relay system 200 may induce a channel in achannel matrix not to have a ‘0’ value by constellation rotating achannel, used in transmitting to the destination, when configuring avirtual MIMO channel, and full diversity gain is acquired.

Also, the constellation rotation relay system 200 of an exemplaryembodiment of the present invention may acquire both gain of a higherdata transmission rate and full diversity gain by compensating for adecrease of diversity gain of a protocol whose data transmission rate iscomparatively greater with constellation rotation, and subsequentlyperformance of a relay network may be enhanced.

The constellation rotation relay method according to the above-describedexemplary embodiment of the present invention may be recorded incomputer-readable media including program instructions to implementvarious operations embodied by a computer. The media may also include,alone or in combination with the program instructions, data files, datastructures, and the like. Examples of computer-readable media includemagnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD ROM disks and DVD; magneto-optical media suchas optical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory, and the like. The media mayalso be a transmission medium such as optical or metallic lines, waveguides, etc. including a carrier wave transmitting signals specifyingthe program instructions, data structures, etc. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter. The described hardware devices may beconfigured to act as one or more software modules in order to performthe operations of the above-described exemplary embodiments of thepresent invention.

According to an exemplary embodiment of the present invention, there isprovided a constellation relay system and a constellation relay methodwhich induces a channel in a channel matrix to prevent a ‘0’ value byconstellation rotating a symbol, transmitted from a source, whenconfiguring a virtual MIMO channel.

Also, according to an exemplary embodiment of the present invention,there is provided a constellation relay system and a constellation relaymethod which induces a channel in a channel matrix to prevent a ‘0’value by constellation rotating the channel, used in transmitting thesymbol to a destination, when configuring a virtual MIMO channel, andacquiring full diversity gain.

Also, according to an exemplary embodiment of the present invention,there is provided a constellation relay system and a constellation relaymethod which can acquire both gain of a higher data transmission rateand full diversity gain by compensating for a decrease of diversity gainof a protocol whose data transmission rate is comparatively greater withconstellation rotation, and subsequently performance of a relay networkmay be enhanced.

While the invention has shown and described with reference to certainexemplary embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims and their equivalents.

1. A constellation rotation relay system comprising: a matrix creatorfor creating a symbol matrix comprising a first symbol to be transmittedduring a first time slot and a second symbol to be transmitted during asecond time slot, such that the first symbol and the second symbol arearranged in parallel in the symbol matrix; and a constellation rotationunit for constellation rotating the symbols in the symbol matrix bymultiplying a 2×2 constellation rotation matrix with the created symbolmatrix to generate a 2×1 constellation rotated symbol matrix, whereinthe matrix creator creates a channel matrix by configuring a parallellink channel for transmitting the constellation rotated symbols to adestination of the relay network, and the constellation rotation unitconstellation rotates a channel in the channel matrix into another valueexcept for 0 by considering the constellation rotated symbol.
 2. Thesystem of claim 1, wherein the constellation rotation unit determinesthe constellation rotation matrix as any one of $\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}},$ where ρ is a numerical value based on a bit energy tonoise ratio or a bit error rate (BER).
 3. A constellation rotation relaysystem comprising: a matrix creator for creating a channel matrix thatis based on a symbol matrix that comprises a first symbol to betransmitted during a first time slot and a second symbol to betransmitted during a second time slot, wherein the first symbol and thesecond symbol are arranged in parallel in the symbol matrix, and basedon a link channel on which the symbols are to be transmitted; and aconstellation rotation unit for constellation rotating a channel in thechannel matrix to another value except for 0 by multiplying a 2×2constellation rotation matrix with the created channel matrix.
 4. Thesystem of claim 3, wherein the symbol to be transmitted to thedestination corresponds to x₁ through a link h_(SD), which links asource of the relay network to the destination, in a first time slot,and corresponds to x₂ through the link h_(SD), and x₁ through a linkh_(RD) which links a relay of the relay network to the destination, in asecond time slot.
 5. The system of claim 4, wherein the matrix creatorcreates $\quad\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}$ as the channel matrix when an output of the destinationassociated with the symbol corresponds to ‘y_(D,1)=h_(SD)*x₁’ in thefirst time slot, and corresponds to ‘y_(D,2)=h_(RD)*x₁+h_(SD)*x₂’ in thesecond time slot.
 6. The system of claim 3, wherein the constellationrotation unit determines the constellation rotation matrix as any one of$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}},$ where ρ is a numerical value based on a bit energy tonoise ratio or a bit error rate (BER).
 7. A constellation rotation relaymethod comprising: creating a symbol matrix comprising a first symbol tobe transmitted during a first time slot and a second symbol to betransmitted during a second time slot, such that the first symbol andthe second symbol are arranged in parallel in the symbol matrix;constellation rotating the symbols in the symbol matrix by multiplying a2×2 constellation rotation matrix with the created symbol matrix togenerate a 2×1 constellation rotated symbol matrix; and creating achannel matrix by configuring a parallel link channel, the parallel linkchannel for transmitting the constellation rotated symbols to adestination of the relay network; and constellation rotating a channelin the channel matrix to another value except for 0, according to therotated constellation.
 8. The method of claim 7, wherein theconstellation rotating the symbol in the symbol matrix comprisesdetermining the constellation rotation matrix as any one of$\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}},$ where ρ is a numerical value based on a bit energy tonoise ratio or a bit error rate (BER).
 9. A constellation rotation relaymethod comprising: creating a channel matrix that is based on a symbolmatrix that comprises a first symbol to be transmitted during a firsttime slot and a second symbol to be transmitted during a second timeslot, wherein the first symbol and the second symbol are arranged inparallel in the symbol matrix, and based on a link channel on which thesymbols are to be transmitted; and constellation rotating a channel inthe channel matrix to another value except for 0 by multiplying a 2×2constellation rotation matrix with the created channel matrix
 10. Themethod of claim 9, wherein the symbol to be transmitted to thedestination corresponds to x₁ through a link h_(SD), which links asource of the relay network to the destination, in a first time slot,and corresponds to x₁ through a link h_(RD), which links x₂ through thelink h_(SD) and a relay of the relay network to the destination.
 11. Themethod of claim 10, wherein the creating of the matrix comprisescreating $\quad\begin{bmatrix}h_{SD} & 0 \\h_{RD} & h_{SD}\end{bmatrix}$ as the channel matrix when an output of the destinationassociated with the symbol corresponds to ‘y_(D,1)=h_(SD)*x₁’ in thefirst time slot, and corresponds to ‘y_(D,2)=h_(RD)*x₁+h_(SD)*x₂’ in thesecond time slot.
 12. The method of claim 9, wherein the constellationrotating of the channel in the channel matrix comprises determining theconstellation rotation matrix as any one of $\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix},\begin{bmatrix}1 & ^{{j\pi}/4} \\1 & {- ^{{j\pi}/4}}\end{bmatrix},{and}$ ${\frac{1}{\sqrt{1 + \rho^{2}}}\begin{bmatrix}\rho & 1 \\{- 1} & \rho\end{bmatrix}},$ where ρ is a numerical value based on a bit energy tonoise ratio or a bit error rate (BER).
 13. A computer-readable storagemedium storing a program for implementing a constellation rotation relaymethod comprising: creating a symbol matrix comprising a first symbol tobe transmitted during a first time slot and a second symbol to betransmitted during a second time slot, such that the first symbol andthe second symbol are arranged in parallel in the symbol matrix;constellation rotating the symbols in the symbol matrix by multiplying a2×2 constellation rotation matrix with the created symbol matrix togenerate a 2×1 constellation rotated symbol matrix; and creating achannel matrix by configuring a parallel link channel, the parallel linkchannel for transmitting the constellation rotated symbols to adestination of the relay network; and constellation rotating a channelin the channel matrix to another value except for 0, according to therotated constellation.
 14. A source node for transmitting data to adestination node, the source node comprising: a matrix creatorconfigured to create a symbol matrix comprising a first symbol to betransmitted by the source node during a first time slot and a secondsymbol to be transmitted by the source node during a second time slot,such that the first symbol and the second symbol are arranged andrepresented in parallel in the symbol matrix; and a constellationrotation unit configured to constellation rotate the first symbol andthe second symbol represented by the symbol matrix by multiplying aconstellation rotation matrix to the created symbol matrix to generate a2×1 constellation rotated symbol matrix.
 15. The source node of claim14, further comprising a transmitter to transmit the constellationrotated first symbol to a relay node and to a destination node.
 16. Thesource node of claim 15, wherein the transmitter transmits theconstellation rotated second symbol to the destination node.
 17. Thesource node of claim 14, wherein the symbol matrix comprises$\begin{bmatrix}x_{1} \\x_{2}\end{bmatrix},$ and the constellation rotated symbol matrix comprises$\begin{bmatrix}{\overset{\sim}{x}}_{1} \\{\overset{\sim}{x}}_{2}\end{bmatrix}.$
 18. The source node of claim 14, wherein the matrixcreator is further configured to create a channel matrix based on thesymbol matrix and based on a link channel on which the symbols are to betransmitted, and the constellation rotation unit is further configuredto constellation rotate the created channel matrix.